HERMS CP plans v1.0 - Review?

[egurney]

I was hoping that somebody that has been through this before could review the 1.0 version of my plans for a HERMS CP. This is a functional diagram only - fuses and such will be added when I complete this phase and start working on the wiring phase.
I plan on have a HLT/HEX combo with the March pump doing the circulation to the MLT. In the HLT there will be a stirrer, IC, and a float switch to try and protect the element. Currently planning a 4500W element in the HLT, and 5500 in the BK.
There will be a selector switch to apply power to only one of the elements at a time regardless of what the PIDs are trying to do.
Will be running off 30A 220V GFCI circuit.

R = Relay
C = Contactor
I = Indicator

Thanks in advance to any and all responses.

 

[Ohio-Ed]

Looks kinda familiar

I'm no expert, but I'll try to have a look a little later tonight.

At a quick glance... You have a PID for the MLT with no control lines. Is that just to monitor temps or is something missing.

Also looks like you are using contactors to disable the SSR's to the elements... could you just switch the SSR control lines instead?

Help me understand why it looks like you have to contactors c2 & c4 in series?

Ed

 

[egurney]

I did borrow a lot of ideas from you!

You have a PID for the MLT with no control lines. Is that just to monitor temps or is something missing.

The PID is the cheapest solution I could find to monitor temps in the MLT @ the CP.

Also looks like you are using contactors to disable the SSR's to the elements

I felt safer having the contactor's switching the 120 legs as I read somewhere the SSR's tend to fail closed.

Help me understand why it looks like you have to contactors c2 & c4 in series

C2 gets activated by the selector switch,
C4 gets activated by the float switch and the NC relay R2. I suppose if the float switch is normally closed I can just wire this directly to the contactor and skip the relay - I'll have to check what my options there are.
This allows both legs to be shut off in either situation.

 

[Ohio-Ed]

A couple more thoughts...

If you are not opposed to using a laptop/pc a bcs-460 is $187, not much more than the 3 PIDs you are talking about and you would get a 4th PID plus all the other cool stuff.

Next thought... I wonder how many SSR's really fail in operation? I know it can happen, but my guess is that most from here are damaged by being mis-wired, etc. My point is you are putting in contactors to protect elements that don't cost much more than the contactors let alone the space required in your control box. Obviously, I went the route of just switching the SSR control

I would wire the float switch in series and eliminate the extra contactor.

 

[diatonic]

A couple more thoughts...

If you are not opposed to using a laptop/pc a bcs-460 is $187, not much more than the 3 PIDs you are talking about and you would get a 4th PID plus all the other cool stuff.

Next thought... I wonder how many SSR's really fail in operation? I know it can happen, but my guess is that most from here are damaged by being mis-wired, etc. My point is you are putting in contactors to protect elements that don't cost much more than the contactors let alone the space required in your control box. Obviously, I went the route of just switching the SSR control

I would wire the float switch in series and eliminate the extra contactor.

+1 to wiring the float switch in series to the contactor. If SSRs aren't adequately cooled they pretty much will fail in an energized state. It happened to me on my first rig when the SSR lost contact with the heatsink. (Long story)

 

[egurney]

bcs-460

I went back-and-forth on the industrial look/BCS. I sit at a computer all day and liked the more manual process industrial look better.

As far as the contactors go, the float switch is 120V so the contactor seemed the best solution.
16 bucks each for the other two seems like pretty cheap insurance. I'd feel safer knowing that if I expect the power to be off it will be off. I realize it might be overkill, but...

Assuming we can agree that the contactors are overkill, but I probably will use them anyway - do you think that the design will work?

 

[Ohio-Ed]

I went back-and-forth on the industrial look/BCS. I sit at a computer all day and liked the more manual process industrial look better.

As far as the contactors go, the float switch is 120V so the contactor seemed the best solution.
16 bucks each for the other two seems like pretty cheap insurance. I'd feel safer knowing that if I expect the power to be off it will be off. I realize it might be overkill, but...

Assuming we can agree that the contactors are overkill, but I probably will use them anyway - do you think that the design will work?

We can agree...

If I understand your reasoning for using the contactors, something you might want to consider... How do you turn both contactors off to the elements? Your selector switch is HLT/BK, one or the other will have power to the SSR when the panel is on.

You have the indicators in series with the pump and stir motor. I'd wire them more like the indicators on the heat element. I don't think you want to pull all the current through the indicator.

How about a float switch for the BK just like the HLT? You can start heating as soon as the BK is full to the switch without fear of a dry fire.

I would eliminate c4 and wire the float switch in series with c2.

I can hardly wait to see v1.1

 

[egurney]

Your selector switch is HLT/BK, one or the other will have power to the SSR when the panel is on.

I was planning on having this as a 3 way. HLT - Off - BK

You have the indicators in series with the pump and stir motor

Good catch - I will definitely make that change

How about a float switch for the BK just like the HLT

I was thinking about that. I keep going back and forth as to whether V1.0 will have an electric BK or not. I'll add it to the diagram.

I would eliminate c4 and wire the float switch in series with c2.

Just to be clear. The output from the HLT side of the selector switch would be wired to the float switch which would in turn be wired to C2? If I understand you correctly, I like it. Same solution less $.

Let me know if I'm understanding the last part correctly. If so I will amend my diagram to reflect those changes and will add the same to the BK.

Thanks,
Eric

 

[Ohio-Ed]

I was planning on having this as a 3 way. HLT - Off - BK


Good catch - I will definitely make that change


I was thinking about that. I keep going back and forth as to whether V1.0 will have an electric BK or not. I'll add it to the diagram.


Just to be clear. The output from the HLT side of the selector switch would be wired to the float switch which would in turn be wired to C2? If I understand you correctly, I like it. Same solution less $.

Let me know if I'm understanding the last part correctly. If so I will amend my diagram to reflect those changes and will add the same to the BK.

Thanks,
Eric

Correct... I would wire the selector switch and the float in series so both have to be on before the coil of your contactor is energized.

I notice no "Hand/Off/Auto" switches for the elements... your only control with be through the PIDs. Certainly not a requirement.

 

[egurney]

I notice no "Hand/Off/Auto" switches for the elements.

I thought all the control I would need would be Off or PID. What is the Hand/Off/Auto switch used for?

 

[pickles]

"Hand" is manual. It allows you to energize pumps, elements, valves etc. by bypassing the automated control (i.e. PID, BCS, BrewTroller).

 

[egurney]

"Hand" is manual.

I don't see the need for that in my system. Everything except the elements are either Hand or Off (no auto) and I don't see why I would need to energize the elements without using the PID.
Unless I am missing something...

 

[Ohio-Ed]

I don't see the need for that in my system. Everything except the elements are either Hand or Off (no auto) and I don't see why I would need to energize the elements without using the PID.
Unless I am missing something...

As I said... certainly optional.
With PIDs in the panel, you will have far less need than I do with the BCS. My PC sits away from the rig, panel is at the rig. The Hand/Off/Auto switches, give me control while standing in front of the rig... if I want to turn on or off a pump or warm up some water (primarily for cleaning or something where no control is required). They are easy switches to add during the design is the only reason I mentioned it.

Ed

 

[egurney]

As I said... certainly optional.

I definitely see where you would want them with your BCS system, but I think I'll have all the control I need...

Now to get to work on 1.1

BTW, thanks for all of your help. Now and in the past - reading through your build was very informative...
Thanks for CodeRage too...

 

[Ohio-Ed]

I definitely see where you would want them with your BCS system, but I think I'll have all the control I need...

Now to get to work on 1.1

BTW, thanks for all of your help. Now and in the past - reading through your build was very informative...
Thanks for CodeRage too...

You're welcome.

My input is simply from someone that went through a similar process, not from an expert point of view. I'm thinking CodeRage or one of the other experts may chime in here and give you (and me) a better/more thorough review.

 

[egurney]

What would be the best way to put an indicator light that would illuminate when the float switch opened - indicating low water level?

 

[Ohio-Ed]

What would be the best way to put an indicator light that would illuminate when the float switch opened - indicating low water level?

Do you have the switch in hand? I think some of those have two sets of contacts... NO and NC, if so, you could use the the NO for the indicator.

 

[egurney]

Do you have the switch in hand?

Nope, I wanted to get everything designed before I started to make purchases...
I'm pretty sure there are either NO or NC, not both.
I'll see if I can find the specs online.

 

[egurney]

The ones on McMaster are either NC or NO. But I was able to find others that are SPDT which would allow me to have the indicator.
http://www.liquidlevel.com/products_switches_standard_vt_LS-11-040.asp

I'll have to add that to 1.1 as well.

 

[Walker]

Assuming we can agree that the contactors are overkill, but I probably will use them anyway - do you think that the design will work?

We can agree...

I don't think contactors are overkill in any way. I see them as a very reasonable safety item.

As mentioned, SSRs can fail so you're better off having a way to manually and definitely kill both hot lines going to the element. True, they might not fail often in the real word, but I'd rather keep my life than save a couple of dollars. I'm not a lucky guy, so....

You could cut the power with a heavy duty DPST rocker or toggle switch, but that means you have to physically touch a switch that is passing high amps and voltage through it, whereas the contactor separates you from the high volts and amps by letting you cut both legs via a low amp and lower voltage SPST switch.

I was originally going to use a hefty toggle for my kill switch, but it cost the same as a contactor and ligther weight switch, so I went with safety, plus I was able to find contactors for only $8. This, combined with only needing one SSR for the actual control process made a contactor + SSR much cheaper than two SSRs.

After assembling my box, which has all controls attached to the hinged door, I realized that the hefty toggle would have been a major PITA. I would have needed big fat stiff wire coming out of the box and to the switch on the door. Opening and closing the door could have been an issue.

Anyway... my $0.02

 

[egurney]

overkill

OK, so maybe not overkill, but not required for this to work.

I'm definitely keeping them in, but thank to Ohio-Ed, I won't be needing as many as in the original design.

plus I was able to find contactors for only $8.

Can you name your source?

So, Walker, what/when is the next update to your image?

 

[Walker]

Can you name your source?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220521443108&ssPageName=STRK:MEWNX:IT

$6 a piece. $5 shipping for one, $1 for each additional.

I bought three of them, so the total was $25.... $8.33 each.

So, Walker, what/when is the next update to your image?

I don't know. There are no major holidays on the horizon, but I am going to a Mexico for a wedding next month, so I might throw on a nice sombrero or a poncho or something.

 

[egurney]

Thanks,
Cinco de Mayo is coming up, that would fit with the Mexican theme!

 

[Ohio-Ed]

I don't think contactors are overkill in any way. I see them as a very reasonable safety item.

As mentioned, SSRs can fail so you're better off having a way to manually and definitely kill both hot lines going to the element. True, they might not fail often in the real word, but I'd rather keep my life than save a couple of dollars. I'm not a lucky guy, so....

You could cut the power with a heavy duty DPST rocker or toggle switch, but that means you have to physically touch a switch that is passing high amps and voltage through it, whereas the contactor separates you from the high volts and amps by letting you cut both legs via a low amp and lower voltage SPST switch.

I was originally going to use a hefty toggle for my kill switch, but it cost the same as a contactor and ligther weight switch, so I went with safety, plus I was able to find contactors for only $8. This, combined with only needing one SSR for the actual control process made a contactor + SSR much cheaper than two SSRs.

After assembling my box, which has all controls attached to the hinged door, I realized that the hefty toggle would have been a major PITA. I would have needed big fat stiff wire coming out of the box and to the switch on the door. Opening and closing the door could have been an issue.

Anyway... my $0.02

Just to be clear... I never used the words "Over Kill" .
I absolutely agree a contactor is a good idea to cut power to the panel and he has one drawn in his e-stop circuit.

As for the other contactors, I do think the benefit is marginal considering the space requirement and additional cost.


Ed

 

[Walker]

Just to be clear... I never used the words "Over Kill" .
I absolutely agree a contactor is a good idea to cut power to the panel and he has one drawn in his e-stop circuit.

As for the other contactors, I do think the benefit is marginal considering the space requirement and additional cost.

I think I know what confused me. For some reason my browser isn't displaying the image from the 1st post, and now it seems that the references to "overkill" were not in regards to the presence of a contactor, but rather the presence of multiple ones with little value.

My bad. I wish I could see the damned image!

Thanks,
Cinco de Mayo is coming up, that would fit with the Mexican theme!

Ah! Yes... Muchas Gracias!

 

[egurney]

Just to be clear... I never used the words "Over Kill"

I agree, I threw that word out there.

But with v1.1 that I'm working on, the contactors will not really be extra. The float switches put out a 120V signal, making the contactors more relevant in the design.

 

[Ohio-Ed]

I agree, I threw that word out there.

But with v1.1 that I'm working on, the contactors will not really be extra. The float switches put out a 120V signal, making the contactors more relevant in the design.

No worries my friend

I don't think there is an "output signal" from a float switch
I think the voltage you are looking at is the MAXIMUM switching voltage. Not sure if there is a minimum.

Ed

 

[egurney]

I don't think there is an "output signal" from a float switch

Right, what I meant to say was that it is 120V AC while the SSR inputs are DC so I can't use the float to control the SSR - thus the contactor is a good fit for this situation.

 

[Ohio-Ed]

Right, what I meant to say was that it is 120V AC while the SSR inputs are DC so I can't use the float to control the SSR - thus the contactor is a good fit for this situation.

I think it would work with DC.
I think its just a magnet sliding up and down causing a set of contacts to open or close.

 

[egurney]

I've obviously never used them before. Here's the text from McMaster:

All switches operate on 120/240 VAC, unless noted

Although the one with the SPDT looks like it wouldn't work at 120.

Looks like I have some decisions to make...

 

[Ohio-Ed]

Do you have a link to the one you are looking at at mcmaster? I was looking at the other link you posted:

http://www.liquidlevel.com/products_switches_standard_vt_LS-11-040.asp

 

[egurney]

Do you have a link to the one you are looking at at mcmaster?

Here's the page:
http://www.mcmaster.com/#float-switches/=6ktw2r

 

[Ohio-Ed]

Here's the page:
http://www.mcmaster.com/#float-switches/=6ktw2r

I think you'd be fine using most of those with low voltage dc. I think the ratings they show are maximums, obviously you should make sure before you try it.

Your choice... but could be an option if you wanted to avoid another contactor.

 

[egurney]

Do you know what I can use for a low-level indicator should I go the route of controlling the element via the SSR with no contactor? The indicators I was planning on using from Automation Direct are either 120V or 24V, and the output from the Auber SSR is 12V.

 

[egurney]

Can anybody confirm or deny whether this float switch will work with my contactor setup?
I'm looking at the M8600-SPDT

http://madisonco.com/madison/level/LLS-316SS.htm
http://madisonco.com/madison/reference/electrical.htm

 

[Ohio-Ed]

Can anybody confirm or deny whether this float switch will work with my contactor setup?
I'm looking at the M8600-SPDT

http://madisonco.com/madison/level/LLS-316SS.htm
http://madisonco.com/madison/reference/electrical.htm

How about using the PID's alarm circuit instead of wiring it directly in the power circuit? Basically, prevent the PID from turning the element on or shut the element off based on the status of the float switch.

 

[egurney]

ow about using the PID's alarm circuit instead of wiring it directly in the power circuit?

Didn't know that that existed. I thought that the alarms were output only.
What the power requirement there? Is there an indicator on the PID when it goes to that state?

 

[Walker]

The alarms are connected built-in mechanical relays. When the alarm is on, the little relays close and pass whatever signal you have from one side to the other.

But... I am still not following Ed here...


edit: actually I think the two alarms are a little different from each other. One is a relay that will close when the PID signals the alarm. The other is a relay that has two sides: one side is closed when the alarm is signaled by the PID and the other side is close when the relay is NOT signaling the alarm. Either way, the PID sends alarms.

 

[Ohio-Ed]

The alarms are connected built-in mechanical relays. When the alarm is on, the little relays close and pass whatever signal you have from one side to the other.

But... I am still not following Ed here...

Yeh, me either... what the heck is he thinking?

Sorry, half backed thought jumped into my head. You are correct, basically, the alarm is a relay that is set based on the input from the temp probe and not gonna do what I suggested.

However, you could wire the level switch in series with the PID's control output so the SSR never sees the +dc if the float switch contacts are open.

Right?

 

[Walker]

However, you could wire the level switch in series with the PID's control output so the SSR never sees the +dc if the float switch contacts are open.

Right?

Yeah, that sounds right. Talking a little out of my but since I've never seen or messed with a float switch, buf if the float switch is basically like a relay that closes when there is a certain level of water, this idea should work just fine.

edit: I am thinking about buying some float switches now, too. This would be great insurance to make sure that I don't accidentally dry-fire my element. Found some for $2.48 w/ free shipping here:

http://www.suntekstore.com/Liquid-Water-Level-Sensor-Horizontal-Float-Switch-Down.html

edit #2: whoops. that has a temp rating of only 80*F.